Screen header and footer are not responsive

### Describe the feature you'd like to request

I wanted to make the screen responsive by applying width's “scale to fit container” when using my own components.
But it is not reflected in the code output by Figma plugin.
I want the width to be a fixed value and not responsive, so I want it to be output as unset like Gen1.

### Describe your use case and how the feature would improve your experience.

As with Gen1, simply set “Scale to fit container” on Figma to display a responsive screen

### Describe alternatives you've considered

Override with Wrapper at 100% width to make it responsive

### Additional context

_No response_

Start by tracing how the Figma plugin handles “Scale to fit container” for custom components and how that setting appears in generated code. Done means a Figma screen using the setting produces responsive header and footer behavior, while fixed-width output remains unset as in Gen1.

Written by the indexing model from the issue text.